i learned about OS/2 from the 'Doing Windows' series. really recommend it, it's a great read about the history behind all this stuff, the computing landscape of that period, and why OS/2 was a huge achievement.

https://www.filfre.net/2018/06/doing-windows-part-1-ms-dos-a...

the road to "run DOS stuff [without being DOS]" was very long, and paved with many gravestones... i think OS/2 comes in in part 5 or 6, but i really recommend reading the whole thing.